This invention relates to circuit interrupters, and more specifically relates to a novel puffer-type circuit interrupter in which a blast of electronegative gas is forced through separating contacts by a nozzle surrounding the interrupter contacts. Gas is forced through the nozzle by virtue of a piston and cylinder arrangement which defines a volume in connection with the nozzle, which volume is reduced when the interrupter is operated to open the interrupter contacts.
Puffer-type interrupters of the type to which the invention relates are shown in the above-referenced applications Ser. No. 712,642 and Ser. No. 702,425 and are also shown in German Published Application 2,363,171. In the above German publication, the main piston of the interrupter is flexibly supported on an auxiliary piston and the cylinder carries a nozzle which is arranged to direct pressurized gas from the interior of the cylinder through the separating contacts of the interrupter. In an arrangement of this type, it is possible to reduce the operating force for operating the cylinder and interrupter contacts during contact interruption as compared to the forces required if the unit had only a single piston. However, in the above arrangement, the operating mechanism must be capable of supplying enough force to overcome the spring force of the flexible coupling between the main and auxiliary pistons.
The spring force which must be overcome in the above arrangement is at its greatest at the time that the contacts are approaching the end of their opening movement and precisely at the point where the greatest flow of fluid through the interrupting contacts is desired. However, since the spring force is substantially high at this point, the spring opposes the continued movement of the cylinder by the operating mechanism so that the fluid flow from the cylinder is reduced.